Crohn's Disease is a complex condition, with many different clinical presentations. Whilst clinical guidelines are available to advise on appropriate treatment options for patients with two particularly complex subgroups; perianal and ileocaecal Crohn’s disease, there is a lack of evidence to guide specific clinical decisions. This research aims to understand how experts make decisions in this setting, with a view to undertaking further research which would help to produce an account, or potentially clinical guidelines to aid future decision making. Interviews will be undertaken with 6-10 IBD specialists as an initial pilot, using cognitive task analysis methodologies, to assess whether this is an appropriate method for a full study.